Editor’s note: This explainer was requested by subscriber Malvika Kaushik.

The TLDR: Where, oh where does this wretched coronavirus come from? The answer is fraught with political, ideological and scientific baggage—and remains elusive more than a year after the first reported case of Covid. We lay out the debate over the virus’ origins, but offer no definitive answers—since they are none to be had.

Researched by: Sara Varghese and Ragini Puri

Why are we talking about this now?

For three reasons.

One: Over recent months, two big pieces were published by well-known journalists that support the ‘lab leak’ hypothesis—i.e. the virus was manufactured in a lab and then ‘escaped’. The first was a deep dive penned by Nicholson Baker in New York magazine. The second was a Medium essay penned by former New York Times writer Nicholas Wade. Both got a lot of attention since these marked the first time that the theory found traction outside the usual conspiracy theory or China-bashing circles. 

Two: On May 13, an international group of respected scientists published an open letter criticising a report submitted by a WHO team investigating the origins of the virus. There are two leading hypotheses about the virus’ origins—either it escaped from a lab or it jumped from an animal species to humans. But which one is it, they asked:

“The WHO-led team, which included scientists from China and several other countries, reported no definitive proof of either hypothesis. Yet, the scientists wrote, the team nevertheless concluded that an animal origin for the pandemic was the likelier scenario and devoted only four out of the report’s 313 pages to the possibility of a lab accident.”

To be clear: they did not champion the ‘lab leak’ theory, but demanded that it be fully investigated “until we have serious data.” And the letter was a big deal because it was signed by the world’s leading coronavirus experts—and published in the prestigious Science journal.

Big points to note: The WHO report concluded that the probability of the virus jumping from an animal to humans was “likely to very likely”—while the likelihood of a lab accident was “extremely unlikely.” What raised the red flag: The team reached this conclusion even though it never investigated the Wuhan lab—since it was never part of their mandate. And on the very day the WHO report was released, its own Director-General Tedros Adhanom Ghebreyesus said: 

“Although the team has concluded that a laboratory leak is the least likely hypothesis, this requires further investigation, potentially with additional missions involving specialist experts, which I am ready to deploy."

Three: Most recently, the Wall Street Journal accessed a US intelligence report that caused a renewed stir. It revealed that three researchers at China’s Wuhan Institute of Virology became seriously ill in November, 2019—and were hospitalised. Now, no one knows why they got sick, but the timing raised a red flag for proponents of the ‘lab leak theory:

“I’m very doubtful that three people in highly protected circumstances in a level three laboratory working on coronaviruses would all get sick with influenza that put them in the hospital or in severe conditions all in the same week, and it didn’t have anything to do with the coronavirus.”

Plus this: The US government has urged for a fresh investigation into all possible explanations for the virus’ origins. The National Security Council spokeswoman carefully said: “We continue to have serious questions about the earliest days of the Covid-19 pandemic, including its origins within the People’s Republic of China.” The EU too has called for a “transparent investigation” without explicitly mentioning the ‘lab leak’ theory.

Ok, so what is this ‘lab leak’ theory?

Nicholson Baker in New York magazine sums up the most sober version of the theory perfectly: 

“A virus spent some time in a laboratory, and eventually it got out. SARS-CoV-2, the virus that causes COVID-19, began its existence inside a bat, then it learned how to infect people in a claustrophobic mine shaft, and then it was made more infectious in one or more laboratories, perhaps as part of a scientist’s well-intentioned but risky effort to create a broad-spectrum vaccine. SARS-2 was not designed as a biological weapon. But it was, I think, designed.”

And what’s the evidence for this?

To be clear, there is no hard evidence supporting this theory. All we have are uncomfortable questions and suggestive facts—and some more compelling than others.

One: China contemplated weaponising coronaviruses in an official document written by health officials and scientists back in 2015:

“The paper says the SARS coronaviruses were heralding a ‘new era of genetic weapons’ that could be ‘artificially manipulated into an emerging human-disease virus, then weaponised and unleashed in a way never seen before.’ It discusses new advancements like freeze-drying micro-organisms that allow biological agents to be stored and later aerosolised them during attacks.”

But, but, but: one official report among hundreds is not exactly damning proof of future policy.

Two: The lead scientist at the Wuhan lab—Dr. Shi Zheng-li or “Bat Lady”—co-wrote a paper with a US researcher that focused on enhancing the ability of bat viruses to attack humans. The aim: to “examine the emergence potential” (the potential to infect humans) of such viruses. According to this published research, their “manufactured virus was able to infect the cells of the human airway, at least when tested against a lab culture of such cells.” And her initial fear when the virus struck was that it had come from her lab. As Baker puts it:

“If one of the first thoughts that goes through the head of a lab director at the Wuhan Institute of Virology is that the new coronavirus could have come from her lab, then we are obliged to entertain the scientific possibility that it could indeed have come from her lab.”

But, but, but: The naysayers point to other countervailing facts:

• The human coronavirus is 96% similar to a bat virus identified in 2013. So there’s no reason it could not have mutated to its present form.
• And in 2017, scientists warned of a new and dangerous coronavirus found in horseshoe bats in caves in the Yunnan province. So it isn’t like we didn’t see this coming.
• The human coronavirus is not related to the bat virus (RaTG13) being studied in Wuhan: “But RaTG13 could not be the source because it differed from the human SARS-2 virus by more than a thousand nucleotides.”

Three: There are multiple changes required for a virus to jump from bats to humans via natural evolution:

“Viruses don’t just make one time jumps from one species to another. The coronavirus spike protein, adapted to attack bat cells, needs repeated jumps to another species, most of which fail, before it gains a lucky mutation.”

But the human coronavirus doesn’t display that many alterations. Hence, it required human intervention to become “well adapted to human cells.”:

“SARS-2 seems almost perfectly calibrated to grab and ransack our breathing cells and choke the life out of them. ‘By the time SARS-CoV-2 was first detected in late 2019, it was already pre-adapted to human transmission,’ [scientist] Alina Chan and her co-authors have written, whereas SARS, when it first appeared in 2003, underwent ‘numerous adaptive mutations’ before settling down.”

Adding to this theory: Scientists around the world are working on ways to make viruses more infectious to humans—to identify and test potential vaccines. And someone may have spliced genetic material from one such experiment on to a bat virus:

“No conspiracy—just scientific ambition, and the urge to take exciting risks and make new things, and the fear of terrorism, and the fear of getting sick. Plus a whole lot of government money.”

But, but, but: Another key scientific paper points out that the mutations on the human coronavirus (SARS-2) aren’t exactly efficient shortcuts:

“‘We do not believe any type of laboratory-based scenario is plausible,’ the scientists said. Why? Because molecular-modeling software predicted that if you wanted to optimize an existing bat virus so that it would replicate well in human cells, you would arrange things a different way than how the SARS-2 virus actually does it—even though the SARS-2 virus does an extraordinarily good job of replicating in human cells.”

Also this: As this paper points out, SARS-2 can infect all sorts of species, not just humans—so where’s the specialisation?

“That SARS-CoV-2 can readily transmit to other animals (pangolins, mink, cats, and others) is strongly indicative [that] this generalist property evolved in the bat reservoir species and not as a consequence of adaptation to human–human transmission.”

PS: There’s much more on the above point that involve ‘furin cleavage sites’ and ‘codons’ which are too nerdy to get into. Both Wade and Ethan Siegel in Forbes make points and counterpoints.

Four: What about those scientists who fell ill in Wuhan?

But, but, but: The Wuhan Institute of Virology conducted blood tests on Dr. Shi Zhengli’s research team—and found “no SARS-CoV-2 antibodies, which would indicate a current or past infection.” Of course, they haven’t shared that data for anyone else to verify.

The bottomline: On the one hand, we are asking a question that may never have a definitive answer—given the high geopolitical stakes involved. As scientist Alina Chan says:

“I don’t know if we will ever find a smoking gun, especially if it was a lab accident. The stakes are so high now. It would be terrifying to be blamed for millions of cases of COVID-19 and possibly up to a million deaths by year end, if the pandemic continues to grow out of control… At this rate, the origin of SARS-CoV-2 may just be buried by the passage of time.”

OTOH, Chan also told NPR:

“This time it's China that's in the hot spot. ... But next time, maybe it's not China. So, if we decide that we cannot investigate, we just give up this time, then other countries might feel that there isn't an accountability mechanism in place.”

But what resonates most is this argument from those calling for an investigation:

“I'm not saying that I am certain that COVID-19 stems from an accidental lab leak, but it would be absolutely irresponsible and could only be politically motivated to say that it's not even worth having a full investigation.”

Reading list

Nicholas Wade and Nicholson Baker make the strongest arguments in favour of the lab leak hypothesis. Ethan Siegel in Forbes offers the most comprehensive counter-argument. New York Times and LA Times have the best reporting on the letter pushing for an investigation into the lab leak theory. NPR has more on the politics surrounding the letter. The Week reports on the 2015 Chinese document on weaponising coronaviruses. We did an explainer on the WHO investigative team, and National Geographic has the best piece on the political fallout over its report.